The present invention relates to audio cables used for interconnecting components in high fidelity applications and, more particularly, to a two conductor audio cable having no delay from end to end as a function of the frequency of audio signals conducted therethrough comprising, a first elongated cylindrical core member of a flexible insulating material extending between the ends of the cable; a plurality of first strands of an electrical conducting material longitudinally disposed between the ends of the cable along the outer surface of the first core member, the first strands being electrically insulated from one another; a first cylindrical support tube of a flexible insulating material disposed over the first core member and extending between the ends of the cable; first support means for supporting the first support tube concentrically about and spaced from the first core member; a second elongated cylindrical core member of a flexible insulating material extending between the ends of the cable; a plurality of second strands of an electrical conducting material longitudinally disposed between the ends of the cable along the outer surface of the second core member, the second strands being electrically insulated from one another; a second cylindrical support tube of a flexible insulating material disposed over the second core member and extending between the ends of the cable; second support means for supporting the second support tube concentrically about and spaced from the second core member; and, flexible electrical shield means disposed around the first and second support tubes and extending between the ends of the cable for holding the support tubes together in parallel relationship and for providing electrical shielding for the first and second strands.
As with the proverbial chain which is only as strong as its weakest link, a true high fidelity audio system is only as good as its poorest component. The true "audiophile", therefore, assures that all components which produce and transmit the signals representing the final reproduced audio neither lose, modify, or add to those signals.
An often overlooked aspect of a good audio system is the cable or wire used, for example, to connect between turntable, pre-amplifier, power amplifier and the speakers producing the ultimate audio. In fact, these connecting cables are often the "weak link" in an otherwise outstanding audio system. This is largely as a result of the so-called "skin effect" of a broad-band audio signal. When signals at audio frequencies are transmitted through a cable comprising a plurality of conductors, the high frequency components move towards the conductors on the outside of the cable and travel at a faster speed than the lower frequency components which move towards the conductors at the center of the cable and travel at a slower speed. Since the signals of the various components arrive at and drive the speakers at different times, the result is what can best be described as a smearing or smudging of the reproduced sound.
The above-described problem of conventional audio cables and a proposed solution therefor is addressed in U.S. Pat. No. 4,538,023 of Brisson. The approach of Brisson is shown in FIGS. 1 and 2. FIG. 1 is substantially a reproduction of FIG. 1 of the Brisson patent. Brisson's approach is to construct a multi-conductor cable which works within the constraints of the skin effect; that is, to make a short center conductor having conductors therearound which are increasingly longer in length. The idea is to have the time for travel of the various frequencies from end to end be identical by making them travel a length functionally related to the speed of travel. In the Brisson cable, generally indicated as 10 in FIG. 1, there is an insulated center conductor 12 running straight along the center of the cable. Around the center conductor 12 are a plurality of insulated middle conductors 14. As represented by the relative length lines with corresponding numbers of FIG. 2, the middle conductors 14 are longer than the center conductor 12. To make the cable of constant length, the middle conductors 14 are helically wrapped about the center conductor 12. Around the middle conductors 14 are a plurality of multi-wire outer conductors 16. Again, as represented by the relative length lines of FIG. 2, the outer conductors 16 are longer than the middle conductors 14 and the center conductor 12. To make the cable of constant length, the outer conductors 14 are helically wrapped about the middle conductors 14 and the center conductor 12. The entire bundle is held together by an outer plastic casing 18.
As will be appreciated by those skilled in the art, the Brisson approach is better than a standard, multi-conductor wire; but, assumes that the frequencies will conveniently divide into three groups and will take the right paths to arrive at the other end simultaneously. It also assumes that the differences in length between the conductors 12, 14, and 16 is the required difference to make the timing come out equal. The patent doesn't indicate or teach how to calculate the differences in conductor length; therefore, one must assume that Brisson is advocating only "longer" towards the outside on a best guess basis and expecting nothing more than an improvement over straight wire--and not a solution to the problem.
Wherefore, it is the object of the present invention to provide a cable which automatically eliminates the time shift by frequency associated with skin effect.
It is a further object of the present invention to provide a dual conductor audio cable which does not delay signals passing therethrough as a function of their frequency.